Locate the rivets that attach the muffler's end cap to the muffler's body. Using an electric drill, drill out the rivets and pull the end cap off the muffler.
Put on a pair of heavy-duty work gloves and reach into the muffler. Pull out the inner core and as much of the packing material as possible. Place the inner core on a work area and unwrap it carefully. Remove the packing material from the inner core and discard all of the original packing material.
Place a layer of fresh packing material on a clean work surface and lay the inner core on the end of the material. Roll the inner core in the packing material, wrapping the packing around the inner core snugly (but not too tight).
Slide the wrapped inner core into the muffler. Place a thin bead of high-temperature silicone sealant around the inner lip of the muffler's end cap. Place the end cap onto the muffler.
Reattach the end cap to the muffler, using a rivet gun to rivet the end cap in place. Use a shop towel to wipe away any silicon sealant that has leaked out from the space between the end cap and the muffler.
Select a baffle that fits your motorcycle's exhaust pipes or muffler. Use a ruler to measure the pipe or muffler's internal diameter and the actual size of the opening. Use these measurements to select an aftermarket bolt-on baffle. Alternatively, many aftermarket exhaust manufacturers offer baffles made specifically for their exhaust systems.
Remove the mounting screw from the outlet end of the baffle and set it aside. Test-fit the baffle into the end of your exhaust pipe or muffler. Remove the baffle from the pipe or muffler once you have determined that it will fit.
Place a small amount of Silly Putty on the end of the muffler or exhaust pipe. Rotate the baffle so that the mounting screw's hole is facing the Silly Putty. Press the baffle into the Silly Putty until it forms an indentation in the putty. Pull the baffle away and set it aside.
Place an electric drill directly over the center of the mounting screw hole's indentation in the Silly Putty and drill a pilot hole through the Silly Putty and exhaust pipe. Remove the Silly Putty and enlarge the hole, as needed, to fit the mounting screw.
Insert the baffle into the exhaust pipe or muffler, aligning the baffle's mounting hole with the hole that was drilled in the previous step. Insert the mounting screw and tighten it with a screwdriver.
